Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.78	8.630%	$109.4773	$109.48	$109.50	$109.50
Purchase #2	$105.44	4.629%	$110.3208	$110.32	$110.30	$110.30
Purchase #3	$141.94	6.577%	$151.2754	$151.28	$151.30	$151.30
Purchase #4	$178.55	4.205%	$186.058	$186.06	$186.05	$186.10
Purchase #5	$239.72	3.703%	$248.5968	$248.60	$248.60	$248.60
Purchase #6	$97.61	6.142%	$103.6052	$103.61	$103.60	$103.60
Purchase #7	$207.48	7.323%	$222.6738	$222.67	$222.65	$222.70
7 purchase totals =	$1,071.52		$1,132.0073	$1,132.02	$1,132.00	$1,132.10